Professor of Physics

University of Minnesota

Cryogenic Dark Matter Search

The Universe is composed of stuff we see (stars, galaxies, gas clouds) and stuff we don't. Gravitational studies of the motions of the stuff we see indicates that it only makes up about 4% of what's out there. The rest is dark energy and dark matter. The dark matter could be particles created at the Big Bang which are still around today. Although there is indirect astrophysical evidence for dark matter, we hope to capture individual dark matter particles in our germanium detectors. The small signals generated by such interactions can only be detected by shielding ourselves from normal cosmic rays (go deep underground) and by reducing thermal interactions (we run at 0.05 degrees above absolute zero, colder than interstellar space!). CDMS is installed in the Soudan Mine in Northern Minnesota and has been setting the most sensitive limits on the number of dark matter particles in our galaxy for the last decade. The final data set using our regular detectors was published in Science 26 March 2010 Vol. 327. no. 5973, pp. 1619 – 1621. Improved Germanium detectors are installed and are running now in an experiment called SuperCDMS. Eventually they will be moved to a deeper site in Canada, called SNOLab.

For a more visual representation (and musical!) of the CDMS detector, try my YouTube Video or download a better quality file here

An interesting animation of the CDMS shielding and detector created by an undergrad at Case Western.

Compact Muon Solenoid Collaboration

(At CERN in Geneva, Switzerland),
→CMS If the zoo of elementary particles is larger than we expect, there may be supersymmetric particles with masses just beyond what has been possible to make in colliders up to now. The new Large Hadron Collider (LHC) at CERN had a bit of a hiccup (understatement) when it tried to turn on in 2008, but all lights are green for a December 2009 start-up. With its higher center of mass energy, it will create new particles and the CMS experiment will detect them. Indeed, some of the new particles may be the dark matter particles we are looking for in the CDMS experiment. Minnesota is responsible for more than 10,000 channels of new hybrid photodiode readout installed in the hadronic calorimeter (HCAL) of the CMS experiment now at CERN. If you want to find out more about them, you can view a recent talk at IEEE symposium IEEE symposium or download the conference proceeding paper

Assay and Acquisition of Radiopure Materials (AARM)

Collaboration of representatives from underground experiments interested in improving underground science infrastructure. We accomplish this by
1. detailed comparisons of Geant4 and FLUKA simulations with data on cosmogenic and radiogenic neutron backgrounds - closing the loop by improving the physics in the code and distributing it to the community.
2. creating a universal web-accessible materials database with information on radiopurity
3. designing an ultra-sensitive low background counting facility that will characterize backgrounds found in the materials used for shielding and experimental fabrication. The FAARM or Facility for AARM. FAARM paper

Past Experiments

The Brookhaven Muon g-2 Experiment BNL g-2
to determine the anomalous magnetic moment of the muon finished several years ago. In February 2001, we announced a 2.6 sigma discrepancy with the Standard Model. Read about it! We continued to improve our experimental precision with our latest result . A discrepancy with the Standard Model simply means that unknown particles or fields are affecting the precession of the magnetic moment of the muon. It could be the first evidence for supersymmetric particles. If so, how would that fit in with the dark matter question? See Muon g-2 Constraints to SUSY Dark Matter over the Next Decade for those connections. For more detail about the experiment, you can see a talk I gave at Fermilab here. There is still a 3 sigma discrepancy with the standard model; A new g-2 experiment is proposed for Fermilab in the next decade, so Stay Tuned.

Brookhaven E952: The NuMass Experiment to make a direct measurement of the muon neutrino mass using the g-2 storage ring. Some historical plots relating to the status of the muon neutrino mass: Past Experiments and how much better the BNL experiment limit will be. The NuMass Presentation before the BNL PAC: Power Point version (original) or pdf file (some loss of graphic info) Unfortunately, this approved experiment was a casualty of funding cuts. It may be worth resurrecting a version of it for the new Fermilab g-2 experiment when that comes on line.

Email: prisca@physics.umn.edu

Phones:

Minneapolis (612) 626-8917
Soudan Underground Mine (218) 753-6611

Whether looking for Dark Matter or Exploring Quantum Mechanics, you are probing that in which we Live and Move and Have our Being. Go Further Up and Further In.

“The world is charged with the grandeur of God.
It will flame out, like shining from shook foil;
It gathers to a greatness, like the ooze of oil
Crushed. Why do men then now not reck his rod?
Generations have trod, have trod, have trod;
And all is seared with trade; bleared, smeared with toil;
And wears man's smudge and shares man's smell: the soil
Is bare now, nor can foot feel, being shod.
And for all this, nature is never spent;
There lives the dearest freshness deep down things;
And though the last lights off the black West went
Oh, morning, at the brown brink eastward, springs -
Because the Holy Ghost over the bent
World broods with warm breast and with ah! bright wings.”